1. Field of the Invention
This invention relates to a liquid-sealed vibration-proof device mainly used for supporting and bearing a vibration generator such as an engine of an automotive vehicle or the like.
2. Description of Related Art
As a liquid-sealed vibration-proof device, e.g. an engine mount for bearing a vibration generator such as an automotive engine so as not to transmit its vibrations to a vehicle body side, such a device is known that is adapted and constructed so that a partition bisecting a liquid chamber inside the device proper into a main liquid chamber and a subsidiary liquid chamber, and an orifice, through which to bring the main liquid chamber and the subsidiary liquid chamber into communication with each other, is formed in the partition, whereby a vibration damping function is exhibited owing to the fluidization effect of liquid through the orifice between both liquid chambers. Another one appears, wherein the aforementioned partition is further provided with a second diaphragm for the purpose of damping vibrations of different frequencies.
The performance required for the liquid-sealed vibration-proof device as described above is that the orifice length and sectional orifice area of the partition and elasticity moduli of both diaphragms exhibit a desired vibration damping function, and besides, a reliability for maintaining the vibration damping function (sealing property) as well as an assembling property for incorporating the partition into the vibration-proof device proper are parameters of vital importance.
For instance, JP P2000-230600 A discloses a liquid-sealed vibration-proof device, which adopts the construction that a partition consisting of three members of an orifice member, a partition plate member and a second diaphragm is provided, and the partition plate member is fixed at its outer peripheral end by crimping to an attachment fitting of the vibration-proof device proper, on the one hand, while the orifice member is forced, at the outer margin of the upper end thereof, to the outer peripheral end of a vibration-proof base on the liquid chamber side thereby positioning, on the other hand. The functionality and reliability as required are thus ensured, and further an assembling property is enhanced.
According to the liquid-sealed vibration-proof device as described in the foregoing Publication, however, because of the construction that the second diaphragm of the three-member partition is vulcanization-bonded to the orifice member, an extra process step of bonding the second diaphragm to the orifice member is necessitated upon manufacturing and besides, upon employing, the second diaphragm is likely to cause a rubber breakdown at the marginal portion and an adhesive separation at the terminal portion owing to a liquid pressure difference of the liquid chamber ascribable to its adhesiveness performance, so that the device is not necessarily complete and satisfactory in the aspect of reliability.
In order to solve the above-mentioned problems, the present invention is intended to provide such a liquid-sealed vibration-proof device that the three members including the orifice member, partition plate member and second diaphragm constituting the partition are assembled in a non-adhesion condition thereby permitting to satisfy both the functionality and reliability and concurrently to ensure a good assembling property.
More specifically, such a construction of the partition is adopted that the orifice member, the second diaphragm and the partition plate member are formed respectively in separate bodies; and when the partition is assembled, a recessed groove formed in the marginal portion of the second diaphragm is engaged with a hook portion of the orifice member projecting inboard and the bottom wall of the recessed groove is clamped and held between the hook portion and the partition plate member.
According to this construction, because of the structure that the second diaphragm is engaged with the hook portion of the orifice member and besides, the second diaphragm is pinched and pressed between the orifice member and the partition plate member, it is possible to maintain the bonding force (sealing performance) of the three members even under high pressure. Here, since the bonding of the second diaphragm to the other members is conducted at a marginal position linked to the surrounding of the rubber-like elastomer membrane, the functionality of the rubber-like elastomer membrane can be ensured without affecting its elasticity modulus. In addition, because the partition plate member, orifice member and second diaphragm are formed separately and an adhesion step is dispensed with, a manufacture at low cost is feasible and a good assembling property is achieved.
In particular, where the construction that the recessed groove at the marginal portion of the second diaphragm is press-fitted into and engaged with the hook portion of the orifice member is adopted, it is possible to enhance remarkably its sealing performance in cooperation with the clamping construction of the bottom wall of the recessed groove.
Where a further construction is adopted such that the partition plate member is formed at its central opening wall with a support cylinder by axial bending and a whole inner periphery of the marginal portion of the second diaphragm is press-fitted into the support cylinder to be supported, the marginal portion of the second diaphragm is firmly bonded to the other members, whereby the functionality of the second diaphragm as a rubber-like elastomer membrane (lowering function in dynamic spring constant) can be more firmly ensured.
In this case, the construction of the partition plate member is exemplified by the one that a plate-like material is press formed into a support cylinder supporting an inner wall forming the recessed (trough-like) groove of the second diaphragm, a clamping portion clamping the bottom wall of the trough-like groove of the second diaphragm, a forcing portion pressing the orifice member upwardly, and a locking portion locked to an attachment fitting by crimping, linked together in this order from inboard to outboard.
As the construction of the marginal portion of the second diaphragm, such an example can be enumerated that the recessed groove of an upside-open U-shape in cross-section is formed of a longitudinal inside wall linked to the surroundings of the rubber-like elastomer membrane, a longitudinal outside wall formed in its perimeter, and a transverse bottom wall linking between both sidewalls, and into the recessed groove is press-fitted or inserted the hook portion of the orifice member.
The orifice member may be either shaped by subjecting a metal plate material to drawing working and forming an orifice channel at the outer periphery or integrally shaped by mold forming, but from the viewpoint of obtaining an orifice member with a sectional area and a shape as desired, a mold shaped product is preferred. In this case, either metal or synthetic resin may be adopted as a raw material for it. A mold formed product of aluminum for a metal and a molded product of engineering plastic for a synthetic resin can be exemplified.